Microbiology > Enterobacteriaceae > Flashcards

Enterobacteriaceae Flashcards

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1
Q

General characteristics of Enterobacteriaceae

A
  • ferment glucose
  • reduce nitrate to nitrites
  • oxidase negative
  • motile at body temperature
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2
Q

oxidase positive Enterobacteriaceae

A

Plesiomonas

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3
Q

Enterobacteriaceae that are non-motile at body temperature

A

Klebsiella, Shigella, Yersinia

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4
Q

Enterobacteriaceae colony morphology

A

Gram-negative rods, facultatively anaerobic, large moist gray colonies, some mucoid colonies

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5
Q

grow throughout thioglycolate broth tube

A

facultatively anaerobic Enterobacteriaceae

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6
Q

Enterobacteriaceae grow well on which agars?

A

MacConkey, EMB agar, HE agar, XLD agar

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7
Q
  • selective and differential media
  • bile salts and crystal violet to inhibit gram +
  • differential for lactose fermentation
A

MacConkey agar

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8
Q
  • peptone base with lactose and sucrose
  • eosin and methylene blue indicators
  • for the isolation and differentiation of lactose-fermenting and non-lactose-fermenting enteric bacilli
A

EMB agar

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9
Q

Sign of lactose fermentation on EMB agar

A

purple color change

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10
Q

No sign of lactose fermentation on EMB agar

A

colorless colonies

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11
Q
  • bile salts to inhibit gram + and some gram -

- differential for lactose and sucrose fermentation

A

HE agar

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12
Q

non-pathogen growth on HE agar

A

most ferment lactose and sucrose; orange color (low pH)

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13
Q

pathogen growth on HE agar

A

green to blue color; black precipitate due to H2S gas production

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14
Q
  • sodium desoxycholate to inhibit gram + and some gram -
  • sucrose, lactose and xylose(with phenol red indicator)
  • lysine to detect lysine decarboxylation
  • thiosulfate to detect H2S
A

XLD agar

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15
Q

Yellow colonies on XLD agar

A
  • fermenters or those not producing lysine decarboxylase

- E. coli, Citrobacter

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16
Q

Colorless or red colonies on XLD agar

A

likely Shigella

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17
Q

Red colonies with black centers on XLD agar

A
  • were yellow then became red when lysine is decarboxylated

- Salmonella

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18
Q

Virulence factors of Enterbacteriaceae

A

adherence, toxins, invasive enzymes, O, H, K antigens

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19
Q

heat stable antigen located in LPS of cell wall

A

O antigen

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20
Q

flagellar antigen; heat stable

A

H antigen

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21
Q

capsular antigen; heat labile; present in E. coli and Salmonella typhi

A

K antigen

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22
Q

Opportunistic Enterobacteriaceae

A
  • normal flora (E. coli)

- septicemia, wounds, UTI, meningitis

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23
Q

Pathogenic Enterobacteriaceae

A

Salmonella, Shigella, Yersinia enterocolitica

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24
Q
  • pink on MacConkey agar, beta hemolytic on SBA
  • motile, sex pili, fimbriae
  • posses O, H, K antigens
A

Escherichia coli (morphology)

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25
- ferments glucose, lactose, trehalose, and xylose - indole positive, methyl red positive (glucose fermentation via mixed acid pathway) - H2S, DNase, urease, PAD, and citrate negative - IMVC (+ + - -)
E. coli (biochemical reactions)
26
Types of E. coli gastrointestinal infections
Enteropathogenic (EPEC), Enterotoxigenic (ETEC), Enteroinvasive (EIEC), Enterohemorrhagic (EHEC), and Enteroadherent
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- infantile diarrhea, associated with nurseries and daycare | - adhesive, stool contain mucus but no blood
Enteropathogenic (EPEC) E. coli
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- Traveler's diarrhea (tropics and subtropics) - requires large inoculum; contaminated food/water, poor hygiene and sanitation - binds to intestinal microvilli (adhesive) - releases toxins (heat-labile toxin and heat-stable toxin)
Enterotoxigenic (ETEC) E. coli
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Enterotoxigenic E. coli toxins
- heat-labile toxin (LT): A and B units, leads to hypersecretion of fluids - heat-stable toxin (ST): leads to hypersecretion
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- dysentery with direct penetration, invasion and destruction of intestinal mucosa - similar to Shigella but requires more inoculum - watery diarrhea with blood, mucus, WBCs - non-motile and don't ferment lactose
Enteroinvasive (EIEC) E. coli
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- hemorrhagic diarrhea, colitis - hemolytic-uremic syndrome (HUS) - watery to bloody diarrhea (no WBCs) - E. coli O157:H7
Enterohemorrhagic (EHEC) E. coli
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low platelets, hemolytic anemia, kidney failure
hemolytic-uremic syndrome
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- watery to bloody diarrhea can be fatal | - associated with undercooked meat, unpasteurized milk, apple cider, bean sprouts, spinach
Enterohemorrhagic E. coli
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- toxins produced by Shiga toxigenic E. coli (STEC) - include Verotoxin I cytotoxin and Verotoxin II - can be screened for on SMAC plate; does not ferment sorbitol
E. coli O157:H7
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- phage mediated cytotoxin - attacks vero cells, also called Shiga-like toxin - neutralized by Shiga toxin antibodies
Verotoxin I
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E. coli O157:H7 toxin not neutralized by Shiga toxin antibodies
Verotoxin II
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Diagnosing E. coli O157:H7
- stool culture on differential medium with serotyping - screens for toxin - demonstrates a fourfold increase in toxin neutralizing antibody titer
38
Enteroadherent E. coli
includes diffusely adherent (DAEC) and enteroaggregative (EAEC)
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- causes UTI's and diarrheal disease - cystitis in kids, acute pyelonephritis in pregnant women, recurring UTI's, pediatric diarrheal disease (in developing countries)
Diffusely adherent (DAEC) E. coli
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- adheres to small intestine; more than 2 weeks - causes "stacked brick" pattern on cells - watery diarrhea, vomiting, dehydration, abdominal pain - mostly in children
Enteroaggregative (EAEC) E. coli
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Extraintestinal infections of E. coli
UTI's, meningitis, septicemia
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Unpathogenic E. coli
most common cause of UTI's (catheters, etc.)
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- most common in neonates, gain infection just before or during birth, can involve amniotic fluid - has capsule antigen K1
Meningitis (caused by E. coli)
44
Septicemia (caused by E. coli)
may result from urogenital tract infection or from GI source
45
Other E. coli
- Escherichia hermanii (clinical significance not established) - Escherichia vulneris (wound infections)
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Klebsiella, Enterobacter, Serratia, Pantoea, Cronobacter, and Hafnia (source/general infections)
- normal flora of GI tract, soil, water, on plants - opportunistic and nosocomial infections - UTI's, wounds, pneumonia
47
Klebsiella, Enterobacter, Serratia, Pantoea, Cronobacter, and Hafnia (biochemical reactions)
- Simmon's citrate +, Potassium cyanide broth +, no H2S production, no deamination of phenylalanine, urease - - Indole -, methyl red -, Voges-Proskauer +, citrate + (all), - IMVC - - + +
48
- most common Klebsiella isolate; affects lower resp. tract - moist, gray mucoid colonies - polysaccharide capsule (virulence)
Klebsiella pneumoniae
49
- similar to K. pneumoniae | - indole +
Klebsiella oxytoca
50
- isolated from nasal secretions and cerebral abscesses | - plasmid-mediated ESBL's
Klebsiella ozaenea
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- infection of the nasal cavity; intense swelling and malformation of entire face and neck - Africa and South America
Klebsiella rhinoscleromatis (pneumoniae subspecies)
52
Two most commonly isolated Enterobacter species
E. cloacae and E. aerogenes
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Enterobacter (biochemical reactions)
MR -, VP +, most produce lysine decarboxylase (not E. cloacae) and ornithine decarboxylase; infect wounds, urine, blood, CSF
54
Pantoea agglomerans
- similar to K. pneumoniae - motile; lysine, ornithine, and arginine negative - outbreak from contaminated IV fluids
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- associated with neonate meningitis and bacteremia | - brain abscesses, respiratory and wound infections
Coronobacter sakazakii
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- positive ONPG (slow lactose) - DNase - highly resistant to antimicrobials
Serratia
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- prodigiosin (red at room temp) - most clinically relevant Serratia species - opportunistic: UTI's, bacteremia, respiratory nosocomial infections
Serratia marcescens
58
Other Serratia species
- S. liquefaciens, S. ficaria, S. entomophila, S. fonticola - S. rubidaea, S. plymuthica (red at room temp) - S. odorifera (dirty musty odor)
59
Hafnia alvei
- linked to gastroenteritis, can be isolated from stool samples - delayed citrate reaction, two biotypes
60
Hafnia Biotype 1
grows in beer wort of breweries; not clinically isolated
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Hafnia Biotype 2
grown from environmental and human samples
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- isolated from urine, wounds, ear and blood infections - produce swarming on lab media, burnt chocolate odor - positive phenylalanine deaminase, produce H2S - lactose -, urease +
Proteus species
63
Proteus mirabilis
- most commonly isolated Proteus | - indole -, ornithine decarboxylase +, K/A with H2S on TSI
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Proteus vulgaris
indole +, ornithine decarboxylase -, sucrose fermentation = A/A with H2S on TSI
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UTI infections, possibly diarrhea, similar to Proteus
Morganella morganii
66
Providencia species
- high resistance to antimicrobials | - P. rettgeri, P. stuartii, P. alcalifaciens
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urinary tract pathogen, nosocomial outbreaks
Providencia rettgeri
68
nosocomial burn unit outbreaks, no swarming, isolated from urine clutures
Providencia stuartii
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- E. tarda is only pathogen - urea -, lysine decarboxylase +, H2S +, indole +, no growth on citrate - bacteremia and wound infections
Edwardsiella
70
Erwinia and Pectobacterium
plant pathogens
71
- weak urease activity, ferment lactose, grow on Simmon's citrate, MR +, similar to Salmonella - C. freundii hydrolyzes urea and doesn't decarboxylate lysine - Salmonella doesn't hydrolyze urea and decarboxylates lysine
Citrobacter
72
- most common Citrobacter | - nosocomial UTI's, pneumonia, endocarditis, intraabdomial abscesses
Citrobacter freundii
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Citrobacter associated with neonatal meningitis and brain abscesses
Citrobacter koseri
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Citrobacter braakii
nosocomial UTI's
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Primary Enterobacteriaceae Intestinal Pathogens
Salmonella, Shigella, Yersinia
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- gram negative rods, facultative anaerobes - clear, colorless, non lactose-fermenting colonies with black centers (K/A, H2S +) - indole -, VP -, phenylalanine deaminase -, urease -, no growth in Potassium cyanide medium, produce H2S
Salmonella
77
most serious pathogens are Subgroup I (S. typhi, S. choleraesuis, S. paratyphi)
Salmonella enterica
78
Differentiating Salmonella subgroup I members
- lysine decarboxylase rules out S. paratyphi - ornithine decarboxylase rules out S. typhi - trehalose fermentation rules out S. choleraesuis
79
Salmonella enterica virulence factors
- fimbriae required for adhesion to intestines - invasion factor (able to transverse intestinal mucosa) - enterotoxin involved in gastroenteritis
80
Antigenic structures of Salmonella
- O and H antigens - Vi capsular antigen - used in serologic typing
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H antigen
- occur in phase I and II - Phase I not always present but identify particular serotype - Phase II are nonspecific
82
Capsular Vi antigen
similar to capsular K antigen, always present, prevents phagocytosis
83
Salmonella enterica (clinical infections)
- acute gastroenteritis or food poisoning caused by organism (not toxin); milk, poultry, eggs, pet handling - carrier state in gallbladder - nontyphoidal bacteremia, typhoid fever, other fevers
84
Typhoid fever disease course
- ingestion of organism; fever, malaise, anorexia, lethargy begin 9-14 days later (flu-like) - invades and penetrates intestinal mucosa, constipation - enters lymphatic system, sustained in mesenteric lymph nodes - enters blood stream; goes to spleen, liver, bone marrow; engulfed by monocytes and grow intracellularly - released into blood stream again (isolated from blood now); prolonged bacteremia, rose spots on abdomen - invasion of gallbladder and Peyer's patches, bacteria released into bowel (isolated from stool now), long-term infection/necrosis of gallbladder, hemorrhage and perforation of bowel
85
non-typhoidal bacteremia
- prolonged fever with intermittent bacteremia - fever and gastroenteritis with brief bacteremia in kids - transient bacteremia during gastroenteritis or septicemia without gastroenteritis in adults
86
Shigella species
S. dysenteriae (group A), S. flexneri (group B), S. boydii (group C), S. sonnei (group D)
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- Shigella that causes the most serious infections | - primarily in developing countries
Shigella dysenteriae (group A)
88
Shigella flexneri (group B)
second most common Shigella in the United States; associated in men having sex with men pop. and young adults
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Shigella boydii (group C)
most common in developing countries
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most common Shigella isolate in the United States; causes short, self-limiting infections
Shigella sonnei (group D)
91
Shigella species (general characteristics)
- non-motile, non lactose-fermenting (K/A) - don't produce gas (except group B) - urease -, no H2S on TSI, doesn't decarboxylate lysine - S. sonnei is ONPG and ornithine decarboxylase + (S. flexneri is -)
92
Shigella species (clinical infections)
- dysentery (S. dysenteriae) - fever and watery diarrhea (S. sonnei) - requires low inoculum (resistant to stomach acid, spread by fecal-oral route - penetration of mucosal epithelium (Shiga toxin)
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Dysentery (S. dysenteriae)
- most severe Shigella infection | - local inflammation, fever, chills, shedding of intestinal mucosa, mucus, blood, ulcers, tenesmus (prolapsed rectum)
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- H2S - on TSI (K/A) | - isolated on CIN agar or CIN II agar with Aeromonas
Yersinia
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- Class A Bioterrorism agent - causes The Plague; transmitted through rodents (except pneumonic form-respiratory droplets) - gram - coccobacilli resembling a safety pin - negative for motility above 22C, ornithine decarboxylase -
Yersinia pestis
96
- contact with/ingestion of swine, cats, dogs, fecal material - survives at cold temperatures, affects kids and ICP's - acute gastroenteritis, simulates apendicitis - causes erythema nodosum (red nodules on lower legs - cause itching and burning) - motility at 25C, non-motile at 37C - grows at 4C, ornithine decarboxylase +
Yersinia enterocolita
97
- rodents, farm animals, birds, guinea pigs; ingestion of fecal material - caseous swelling called pseudotubercles in mesenteric lymph nodes - motile at 25C; ornithine decarboxylase -
Yersinia pseudotuberculosis
98
- peptone base with yeast extract, mannitol, bile salts, cefsulodin, igrasan, novobiocin, neutral red and crystal violet indicators - selective for Yersinia and Aeromonas
CIN (Cefsulodin-Igrasan-Novobiocin) agar
99
Screen stool pathogens (HE, XLD, Mac, SMAC) for ______
Salmonella, Shigella, Campylobacter, E. coli O157:H7
100
Screen stool pathogens (CIN agar) for ____________
Yersinia
101
Serologic grouping for __________
- Salmonella (60 types of O antigens; agglutination) | - Shigella (A through D serotypes)
Microbiology
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